Radial tires, especially supersized tires such as construction vehicle tires, may suffer a side cut due to a rock, a large protruding object, or the like, and a ply cord in a carcass ply may break along with ply rubber at the sidewall portion. In some cases, the break may also reach the inner liner at the inner side of the tire.
One method for repairing a radial tire damaged in this way is to use a patch rubber constituted by a reinforcement sheet in which a plurality of reinforcing elements (patch cords) arranged in parallel are covered with rubber. The patch rubber is attached with adhesive from the inner side of the tire to the damaged portion of the carcass ply where the ply cord has broken in order to reinforce the damaged portion with the patch cords. A representative conventional technique applying this method will be described with reference to FIG. 8. FIG. 8 is a plan view of the sidewall portion from inside the tire, transparently showing a carcass ply 5a1 and a patch rubber 40 attached to the carcass ply. A tire radial direction is indicated by R. Among a plurality of ply cords 6 in the carcass ply 5a1, a certain number of ply cords 6a are broken. Note that the ply cords 6a extend radially from the inside towards the outside in the tire radial direction R. The rectangular patch rubber 40 attached to the damaged region is a cord rubber cover layer in which a plurality of patch cords 41 arranged in parallel are covered with rubber and vulcanized. The patch rubber 40 is attached to the damaged region so that the patch cords 41 are parallel to a tire radial direction (in FIG. 8, the direction in which the middle ply cord, among the three broken ply cords, extends) and so that the upper side 42a and lower side 42b of the rectangle extend in the tire circumferential direction.
Patent Literature 1 discloses a technique for reinforcement using a patch rubber that includes a metal cord rubber layer portion with a plurality of metal cords covered in rubber, with the patch rubber being attached by embedding this portion in the damaged region in which the carcass ply is broken, so that the metal cords connect the broken portion of the broken ply cords.